Three-transition cascade erbium laser at 1.7, 2.7, and 1.6 microm

We report on an upconversion cascade laser in an erbium-doped ZBLAN fiber emitting simultaneously on the three transitions (4)S(3/2) ? (4)I(9/2) at 1.7 microm , (4)I(11/2) ? (4)I(13/2) at 2.7 microm , and (4)I(13/2) ? (4)I(15/2) at 1.6 microm . At moderate pump powers, the laser transition at 1.6 microm supports 2.7-microm lasing and permits a slope efficiency at 2.7 microm of 15% versus launched pump power. Above the threshold of upconversion lasing at 1.7 microm , the slope efficiency at 2.7 microm increases to 25.4%. Taking pump excited-state absorption into account, this value represents more than 90% of the theoretical slope efficiency. A transversely single-mode output power of 99mW is achieved at 2.7 microm.     

Er：YLF晶体中Er^3＋离子的光谱特征

利用居地－奥非脱（Ｊｕｄｄ－Ｏｆｅｌｔ）理论计算了Ｅｒ＾３＋离了在氟化钇锂（ＬｉＹＦ４简写为ＹＬＦ）晶体中的辐射跃迁几率Ａｊｊ无辐射跃迁几率ωＪＪ及激发态荧光寿命τ，并根据荧光动力学方程计算出各激发态布居数ＮＪ与掺杂浓度ｘ的关系，对２．７μｍ激光（＾４Ｉ１１／２→＾４Ｉ１３／２）来说，掺杂浓度要大于～３ａｔ％，才能实现布居数反转，对波长为１．７３μｍ的＾４Ｉ１３／２→＾４Ｉ１５／２跃迁，存在荧光强     

Infrared frequency upconverter for high-sensitivity imaging of gas plumes

A remote methane detection system has been developed using a single-frequency tunable optical parametric oscillator at 3.4 microm infrared wavelength. The infrared received light is converted by a frequency upconverter with a strong pump beam to near-infrared wavelength at 0.81 microm and detected by a sensitive photomultiplier. The conversion efficiency of the upconverter was 40% for the backscatter signal from a topographic target, and the detector sensitivity was 11 times higher than that of the cooled InAs detector. By raster scanning the infrared beam, imaging was realized for the methane gas plume with an accuracy of 20 parts in 10(6)m at the range of ~2m.     

Upconversion fiber-optic confocal microscopy under near-infrared pumping

We present a simple upconversion fiber-optic confocal microscope design using a near-infrared laser for pumping of a rare-earth-doped glass powder. The nonlinear optical frequency conversion process is highly efficient with more than 2% upconversion fluorescence efficiency at a near-infrared pumping wavelength of 1.55 microm. The upconversion confocal design allows the use of conventional Si detectors and 1.55 microm near-infrared pump light. The lateral and axial resolutions of the system were equal to or better than 1.10 and 13.11 microm, respectively.     

Frequency shifting through cascaded second-order processes in a N-(4-nitrophenyl)- L-prolinol crystal

We exploit the high second-order susceptibility of the organic crystal N-(4-nitrophenyl)-L-prolinol to accomplish, through a cascaded second-order process, wavelength conversion of a signal pulse (from 1.16 to 1.14 microm) under the action of a pump pulse (at 1.15 microm). In a 2.8-mm-thick crystal, wavelength conversion with unit gain was obtained with a pump peak intensity as low as 9 MW/cm(2) . At low intensities, in the limit of negligible conversion where the cascading effect can be described through an effective third-order susceptibility, we derive |(x)((3))(eff) | approximately 2.4 x 10(-17) m(2)/V(2), which is ~10(2) larger than the nonresonant (x)((3)) of conjugated polymers or semiconductors.     

Slot-waveguide biochemical sensor

We report an experimental demonstration of an integrated biochemical sensor based on a slot-waveguide microring resonator. The microresonator is fabricated on a Si3N4-SiO2 platform and operates at a wavelength of 1.3 microm. The transmission spectrum of the sensor is measured with different ambient refractive indices ranging from n=1.33 to 1.42. A linear shift of the resonant wavelength with increasing ambient refractive index of 212 nm/refractive index units (RIU) is observed. The sensor detects a minimal refractive index variation of 2x10(-4) RIU.     

Increasing the imaging depth of coherent anti-Stokes Raman scattering microscopy with a miniature microscope objective

A miniature objective lens with a tip diameter of 1.3 mm was used for extending the penetration depth of coherent anti-Stokes Raman scattering (CARS) microscopy. Its axial and lateral focal widths were determined to be 11.4 and 0.86 microm, respectively, by two-photon excitation fluorescence imaging of 200 nm beads at a 735 nm excitation wavelength. By inserting the lens tip into a soft gel sample, CARS images of 2 microm polystyrene beads 5 mm deep from the surface were acquired. The miniature objective was applied to CARS imaging of rat spinal cord white matter with a minimal requirement for surgery.     

LiYF4:Nd3+中脉冲光泵浦的上转换蓝光

本文报道利用578.4nm的脉冲光泵浦,在室温和77K下,观察到LiYF4:Nd3+单晶中的上转换蓝光。由发光强度与泵浦光强度平方的直线关系,确定此上转换过程是双光子过程.通过对吸收谱和激发谱以及衰减曲线的研究,确定其上转换激发机制为两步激发和能量传递上转换。     

Photonic crystal waveguides utilizing a modulated lattice structure

We experimentally demonstrate a new class of optical waveguide consisting of a-Si/SiO(2) autocloned photonic crystals with modulated lattice structure. The waveguide utilizes the macroscopic form birefringence of photonic crystals and confines light by the difference in the effective refractive index. A monopole modal field with spot diameters of 6.9 micromx6.5 microm was observed at a wavelength of 1.55 microm. The propagation loss of the waveguide at the wavelength was found to be ~4.2 dB/mm at most.     

Er^3+,Cr^3+共掺杂BaAl2Si2O8荧光粉的发光性质及能量传递

利用高温固相法合成BaAl2Si2O8:Cr^3+,Er^3+系列荧光粉,研究了Cr^3+和Er^3+掺杂对BaAl2Si2O8材料发光特性的影响.BaAl2Si2O8:Er^3+荧光样品在393 nm激发波长下只呈现出峰值为550 nm的绿色荧光,来源于2H11/2→4I15/2和4S3/2→4I15/2跃迁的叠加.BaAl2Si2O8:Cr^3+荧光样品在550 nm激发波长下呈现峰值为694 nm的红色荧光,来源于2E→4A2的跃迁.在共掺杂样品BaAl2Si2O8:Cr^3+,Er^3+中,用Cr^3+激发峰的凹槽处380 nm作为激发光,得到的发射峰不仅有Er^3+的发射峰位,还有Cr^3+的发射峰位,说明两个离子之间可能存在辐射能量传递;对共掺杂BaAl2Si2O8:1%Cr^3+,x%Er^3+样品的荧光光谱进行测试,随着x的增加,Cr^3+的激发和发射光谱强度均有所增加,并且当x=0.5时,光谱强度是原来的4倍.另外,当固定Cr^3+的浓度时,随着Er^3+的浓度增加,Cr^3+的荧光寿命逐渐增加;当固定Er^3+的浓度时,随着Cr^3+的浓度增加,Er^3+的荧光寿命逐渐减小.这些现象表明了Er^3+和Cr^3+之间存在共振能量传递,通过理论计算得到Er^3+和Cr^3+之间的能量临界距离为4.5 nm,属于电偶极-电偶极相互作用.     

Er3+掺杂Ge-Ga-S-KBr硫卤玻璃的中红外发光和多声子弛豫的研究

用熔融急冷法制备了系列不同Er3+离子掺杂浓度的Ge-Ga-S-KBr硫卤玻璃,测试了样品折射率、吸收光谱、中红外荧光光谱。通过吸收光谱计算了Er3+离子吸收谱线的振子强度,应用Judd-Ofelt理论计算分析了Er3+离子在Ge-Ga-S-KBr硫卤玻璃中的强度参数Ωi ( i = 2 , 4 , 6) 、自发辐射跃迁几率A、荧光分支比?和辐射寿命?rad等光谱参数。研究了808nm激光泵浦下样品中红外荧光特性与掺杂浓度之间变化关系,并用Futchbauer-Ladenburg公式分别计算了2.8?m处的受激发射截面。结果表明,在808nm 激光泵浦下观察到了2.8?m中红外荧光,分别对应于Er3+： 4I11/2?4I13/2跃迁,当Er3+离子掺杂浓度从0.4wt%增加到1.0wt%时,中红外荧光强度都随相应增加,计算的Er3+:4I11/2?4I13/2跃迁多声子驰豫速率分别为37 s-1。     

掺钕锂铝硅玻璃陶瓷制备和发光性能研究

采用传统熔融及退火技术,引入合适的添加剂于相对低温下成功制备出掺钕锂铝硅玻璃,通过控制成核和析晶工艺制备出锂铝硅玻璃陶瓷。采用差热分析、X射线衍射、扫描电镜、紫外可见近红外分光光度计和荧光光谱仪对材料进行表征。三个发光谱带中心波长位于890 nm,1065 nm和1330 nm处,分别对应于4F3/2→4I9/2,4F3/2→4I11/2和4F3/2→4I13/2跃迁。玻璃陶瓷晶相及晶粒大小对Nd3 离子发光性能影响很大。当Nd3 离子进入晶粒尺寸为10~20 nm的β--锂霞石固溶体时,发光强度与基质玻璃相比明显增强,在1065 nm处的受激发射截面iσn达1.931×10-21cm2,比基质玻璃受激发射截面提高了约8%。当β--锂霞石固溶体晶粒尺寸接近可见光波长时钕离子发生荧光猝灭。而当β--锂霞石固溶体晶型转变为β--黝辉石固溶体时,荧光猝灭消失。     

Wavelength-agile mid-infrared (5-10 microm) generation using a galvano-controlled KTiOPO4 optical parametric oscillator

A wavelength-agile mid-infrared (IR) ZnGeP2 (ZGP) optical parametric oscillator (OPO) using a galvano-controlled double-crystal KTiOPO4 (KTP) OPO was demonstrated. The mid-IR wavelength was tuned by varying the KTP OPO pump wavelength while the ZGP crystal angle remained fixed. Rapid tuning of the KTP OPO was achieved by changing the crystal angle by using the galvano scanner. Our mid-IR source can jump to a different wavelength without scanning through the intermediate wavelengths while also permitting continuous-wavelength scanning. The mid-IR source can be tuned from approximately 5to10 microm at a phase-matching angle of 51 degrees , while the pump wavelength is controlled in the 1.95-2.2 microm range.     

口红的荧光和拉曼光谱特性的研究

人们消费方式的变化促使电商崛起,美妆市场呈爆发式增长,口红产品的安全成为关注焦点。面对品牌口红真伪问题,市场检测化妆品方法单一,对品牌口红的特征无针对性。采用三维荧光技术和共聚焦拉曼技术对某品牌真假口红的光谱性质进行了研究。三维荧光光谱显示五组口红均存在激发光峰值波长为320 nm左右,发射峰波长在372 nm附近的荧光(Ⅰ区)。A1, A2, A3, B1, B2和B3这6个样品中,激发光峰值波长为230 nm时会发出中心波长在400 nm左右的荧光,而在A4, A5, B4和B5这4个样品中,激发光峰值波长红移到250 nm左右,其荧光发射峰也发生了相应的红移,到450～470 nm(Ⅱ区)。此外,A5还存在激发光峰值波长550 nm,发射峰在590 nm附近的荧光;B1还存在270 nm激发,292 nm左右发射的荧光峰(Ⅲ区)。采用荧光强度相对法来定量分析,若都以Ⅰ区的荧光强度为1,口红不同色号间、同色号真假口红间的Ⅱ区和Ⅲ区的相对荧光强度显著不同。拉曼光谱显示正品口红中存在TiO₂的振动峰,也还存在大量的C—C, C—N,—CH₂和...     

High-intensity bowtie-shaped nano-aperture vertical-cavity surface-emitting laser for near-field optics

We report a high-intensity nano-aperture vertical-cavity surface-emitting laser (VCSEL) utilizing a bowtie-shaped aperture. A maximum power of 188 microW is achieved from a 180 nm bowtie aperture at a wavelength of 970 nm. The near-field full width at half-maximum intensity spot size 20 nm away from the bowtie aperture is 64 nm x 66 nm from simulation, and the peak near-field intensity is estimated to be as high as 47 mW/microm(2). This intensity is high enough to realize near-field optical recording, and the small spot size corresponds to storage densities up to 150 Gbits/in(2). The bowtie-aperture VCSEL also enables other applications, such as compact high-intensity probes for ultrahigh-resolution near-field imaging and single molecule fluorescence and spectroscopy.     

Energy transfer and mid-infrared luminescence properties of Tm3+ /Dy3+ codoped chalcohalide glasses

A series of chalcohalide glasses based on the composition 0.9 (Ge25 Ga5 S70)-0.1CsI doped with the different Tm3+ / Dy3+ ions ratio were synthesized by melt-quenching technique. The absorption spectra, and mid-infrared fluorescence of different glass samples under 800 nm laser excitation were measured. The results prove that, Tm3+ is an efficient sensitizer, which can enhance the Dy3+ : 2.9 microm fluorescence intensity significantly. A decrease in the intensity of 1.8 microm fluorescence and lifetimes of the Tm3+ : (3)F4 level occurred with increasing the concentration of Dy3+ ions from 0 to 1 Wt% where Tm3+ concentration was fixed to 0.5 Wt%. Also a wide spectral overlap between Tm+ : 1.8 microm emission and the absorption of Dy3+ : 6 H(15/2) --> (6)H(11/2) showed that the effective energy transfer between the two rare-earth ions was mainly attributed to the resonance energy from Tm3+: (3)F4 to Dy(3)+ : (6)H(11/2) level.     

狭缝微等离子体的光谱线形研究

在狭缝微等离子体中,研究了Ar Ⅰ(2P2→1S5)光谱线的展宽和频移随放电参数的变化.为了测量谱线频移,采用低气压(10 Pa左右)氩气放电发射的Ar Ⅰ光谱线作为参考线.实验在氩气含量为99.92%的氩气/空气放电中,测量了气压从1×104Pa增大到6×104 Pa时Ar Ⅰ谱线的频移和展宽.结果表明随着气压的升高...     

环丙沙星的光谱性质、质子化作用与荧光量子产率

研究了环丙沙星(ciprofloxacin, CIP)在不同pH条件下的荧光光谱、紫外吸收光谱和质子化作用,测量了CIP在中性条件下的荧光量子产率。在H+浓度大于1 mol·L-1的HCl介质中,CIP分子(简写为HL)可以结合3个质子而以H₄L3+形式存在,有微弱的荧光,最大荧光发射波长(λ_ｍａｘ)为456 nm。在pH 0～2的酸性条件下,CIP主要以H₃L2+形式存在,λ_ｍａｘ为450 nm,荧光较弱,荧光强度随pH的升高而上升。在pH 2～4时,CIP主要以H₂L+形式存在,具有强荧光,λ_ｍａｘ仍为450 nm。当pH＞4时,λ_ｍａｘ逐步蓝移到414 nm,荧光强度随pH的升高而稍有降低,同时紫外吸收光谱也有明显变化,表明H₂L+随pH升高而失去质子,以双极离子HL形式存在。当pH＞8时,荧光强度随pH升高而减弱至消失,表明HL逐步失去质子,转化为无荧光的阴离子L-。在分子形态变化过程中,最大荧光激发波长始终在275 nm附近,但最大荧光发射波长有较大变化。在pH 7.0的缓冲溶液中,以硫酸奎宁为参比,测得CIP在最大荧光激发波长275 nm处的荧光量子产率为0.12。     

Use of a single-mode fiber coupler for second-harmonic-generation microscopy

We present a compact second-harmonic-generation (SHG) microscope based on a three-port single-mode fiber coupler. The fiber coupler is used to deliver a near-infrared ultrashort-pulsed laser beam as well as to collect the SHG signal in the visible wavelength range. The SHG microscope exhibits an axial resolution of 1.8 microm, which shows a slight enhancement of the optical sectioning effect compared with that for two-photon excitation at the same excitation wavelength. It is also demonstrated that SHG and two-photon fluorescence images under parallel and perpendicular laser excitation polarization can be simultaneously obtained.     

Low-pump-threshold continuous-wave singly resonant optical parametric oscillator

We describe a compact all-solid-state continuous-wave singly resonant optical parametric oscillator (SRO) with a minimal pump-power requirement. The SRO is based on periodically poled LiNbO(3) as the nonlinear material and is pumped by a 1-W diode-pumped Nd:YVO(4) minilaser at 1.064 microm . By exploiting the intracavity pumping technique in a 50-mm crystal, we have achieved SRO operation threshold at a diode pump power of only 310 mW.At 1 W of input diode power, the SRO delivers 70 mW of output power in the nonresonant idler at 3.66 microm , at a photon conversion efficiency of 55%. Multiparameter tuning of the SRO yields a signal wavelength range from 1.45 to 1.60 microm and an idler wavelength range from 3.16 to 4.02 microm in the mid infrared. The device is characterized by robust turnkey operation and long-term amplitude-stable performance.